In general, an outboard motor widely used in a small boat has a fuel supply unit in order to supply fuel stored in a fuel tank to an engine. In the fuel supply unit, the fuel is pumped by a fuel pump to a fuel injector. As such a fuel pump, there are known an in-tank type fuel pump embedded in a vapor separator or a so-called in-line type fuel pump provided separately from the vapor separator and disposed in the middle of the fuel flow path.
In Patent Literature 1, there is discussed a fuel injection device in which fuel inside a fuel tank is supplied to a vapor separator by using a first fuel pump, so that the fuel under a fuel liquid level formed inside the vapor separator is supplied to a fuel distribution pipe by using an in-line type second electric fuel pump disposed outside the vapor separator, and the fuel is injected and supplied to the engine by using a fuel injection valve installed in the fuel distribution pipe.
In Patent Literature 2, there is discussed an outboard motor fuel supply unit provided with a vapor separator that performs vapor-liquid separation for the fuel supplied from a fuel tank by a low-pressure fuel pump to discharge the fuel vapor to the air, a fuel cooler, and an in-line high-pressure fuel pump connected in the middle of a fuel pipe connected to a side face of the fuel cooler.
In comparison with the in-tank type fuel pump, the in-line type fuel pump makes it possible to reduce the entire size of the outboard motor because individual components can be miniaturized although the number of components increases. In addition, since the fuel pump can be miniaturized, it is possible to allow for freedom in a design of the fuel pump. In addition, it is possible to improve starting performance of the engine by arranging the fuel pump in the vicinity of the fuel injector.